/*
 * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package java.util.jar;

import java.util.zip.*;
import java.io.*;

/**
 * The <code>JarOutputStream</code> class is used to write the contents
 * of a JAR file to any output stream. It extends the class
 * <code>java.util.zip.ZipOutputStream</code> with support
 * for writing an optional <code>Manifest</code> entry. The
 * <code>Manifest</code> can be used to specify meta-information about
 * the JAR file and its entries.
 *
 * @author David Connelly
 * @see Manifest
 * @see java.util.zip.ZipOutputStream
 * @since 1.2
 */
public class JarOutputStream extends ZipOutputStream {

  private static final int JAR_MAGIC = 0xCAFE;

  /**
   * Creates a new <code>JarOutputStream</code> with the specified
   * <code>Manifest</code>. The manifest is written as the first
   * entry to the output stream.
   *
   * @param out the actual output stream
   * @param man the optional <code>Manifest</code>
   * @throws IOException if an I/O error has occurred
   */
  public JarOutputStream(OutputStream out, Manifest man) throws IOException {
    super(out);
    if (man == null) {
      throw new NullPointerException("man");
    }
    ZipEntry e = new ZipEntry(JarFile.MANIFEST_NAME);
    putNextEntry(e);
    man.write(new BufferedOutputStream(this));
    closeEntry();
  }

  /**
   * Creates a new <code>JarOutputStream</code> with no manifest.
   *
   * @param out the actual output stream
   * @throws IOException if an I/O error has occurred
   */
  public JarOutputStream(OutputStream out) throws IOException {
    super(out);
  }

  /**
   * Begins writing a new JAR file entry and positions the stream
   * to the start of the entry data. This method will also close
   * any previous entry. The default compression method will be
   * used if no compression method was specified for the entry.
   * The current time will be used if the entry has no set modification
   * time.
   *
   * @param ze the ZIP/JAR entry to be written
   * @throws ZipException if a ZIP error has occurred
   * @throws IOException if an I/O error has occurred
   */
  public void putNextEntry(ZipEntry ze) throws IOException {
    if (firstEntry) {
      // Make sure that extra field data for first JAR
      // entry includes JAR magic number id.
      byte[] edata = ze.getExtra();
      if (edata == null || !hasMagic(edata)) {
        if (edata == null) {
          edata = new byte[4];
        } else {
          // Prepend magic to existing extra data
          byte[] tmp = new byte[edata.length + 4];
          System.arraycopy(edata, 0, tmp, 4, edata.length);
          edata = tmp;
        }
        set16(edata, 0, JAR_MAGIC); // extra field id
        set16(edata, 2, 0);         // extra field size
        ze.setExtra(edata);
      }
      firstEntry = false;
    }
    super.putNextEntry(ze);
  }

  private boolean firstEntry = true;

  /*
   * Returns true if specified byte array contains the
   * jar magic extra field id.
   */
  private static boolean hasMagic(byte[] edata) {
    try {
      int i = 0;
      while (i < edata.length) {
        if (get16(edata, i) == JAR_MAGIC) {
          return true;
        }
        i += get16(edata, i + 2) + 4;
      }
    } catch (ArrayIndexOutOfBoundsException e) {
      // Invalid extra field data
    }
    return false;
  }

  /*
   * Fetches unsigned 16-bit value from byte array at specified offset.
   * The bytes are assumed to be in Intel (little-endian) byte order.
   */
  private static int get16(byte[] b, int off) {
    return Byte.toUnsignedInt(b[off]) | (Byte.toUnsignedInt(b[off + 1]) << 8);
  }

  /*
   * Sets 16-bit value at specified offset. The bytes are assumed to
   * be in Intel (little-endian) byte order.
   */
  private static void set16(byte[] b, int off, int value) {
    b[off + 0] = (byte) value;
    b[off + 1] = (byte) (value >> 8);
  }
}
